Rockwell Automation 20P PowerFlex Digital DC Drive - Manual (Page 268)

268 Rockwell Automation Publication 20P-UM001I-EN-P - February 2013
Appendix C Application Notes
Example 3: DC Tachometer with Feedback Bypass
This example is similar to example 2 except that it compensates for the loss in
feedback resolution by setting parameter 562 [Anlg Tach Gain].
• Par 175 [Rated Motor Volt] = 500V (default)
• Par 45 [Max Ref Speed] = 1750 rpm (default)
• Set Par 562 [Anlg Tach Gain] = 2.057 (3600/1750)
• Par 585 [Overspeed Val] = 1925 rpm (default)
• Set DIP switch S4 = 180V
This value is set to the next highest DIP switch setting available based on
the result of the following calculation:
• Par 162 [Max Feedback Spd] = 1750 rpm (default)
This value is based on: (180V/50V/2.057) =1.750 (1000)
• The reference and feedback resolution = (5250 fpm/25000 counts) = 0.21
fpm/count
Example 4: DC Tachometer with Field Weakening
This example is similar to example 3 except that a field weakening speed of 2500
rpm is configured rather than a base speed of 1750 rpm.
• Par 175 [Rated Motor Volt] = 500V (default)
• Set Par 45 [Max Ref Speed] = 2500 rpm
• Set Par 562 [Anlg Tach Gain] = 1.44
• Set Par 585 [Overspeed Val] = 2750 rpm
• Set DIP switch S4 = 180V
This value is set to the next highest DIP switch setting available based on
the result of the following calculation:
• Set Par 162 [Max Feedback Spd] = 2500 rpm
This value is based on: (180V/50V/1.44) = 2.5 (1000)
• The reference and feedback resolution = (7500 fpm/25000 counts) = 0.3
fpm/count
Tachometer x Max Motor Speed x Overspeed Percentage = Scaled Tach Input Volts
(50V/1000 rpm) (1750 rpm) (1.1) 96.25V
Tachometer x Max Motor Speed x Overspeed Percentage = Scaled Tach Input Volts
(50V/1000 rpm) (2500 rpm) (1.1) 137.5V